Biology subjects

Uhl, L.

Publications and source records attributed to Uhl, L..

4 recordsLinked to original sources

bioRxiv2025

The MYCN/Aurora-A complex is a cyclin activating kinase for CDK12

Deregulated MYCN is a driver of aggressive pediatric and adult neuroendocrine tumors, but critical oncogenic processes downstream of MYCN remain poorly defined. In neuroblastoma, MYCN interacts with and activates the Aurora-A kinase. Here we show that Aurora-A is a CDK-activating kinase for CDK12 by phosphorylating T893 in the T-loop, thereby enhancing its kinase activity. Aurora-A-dependent activation of CDK12 controls phosphorylation of T4 of RNA polymerase and recruits transcription termination complexes, thereby preventing transcription-replication conflicts. Enhanced crosslinking and immunoprecipitation sequencing reveals that Aurora-A associates with splice sites on nascent RNA. RNA-bound Aurora-A is catalytically inactive. MYCN competes with RNA for binding to Aurora-A and displaces Aurora-A from RNA in cells, promoting its CDK12 kinase activity. Combining Aurora-A and CDK12 inhibition potently suppresses the growth of MYCN-amplified neuroblastoma cells and patient-derived xenografts. Our data demonstrate that an Aurora-A/CDK12-dependent transcription termination pathway is a critical and targetable dependency of MYCN-driven tumors.

cancer biology↗

bioRxiv2024

RNA-mediated MYC multimerization suppresses innate immune signaling

In response to perturbed transcription elongation, the MYC oncoprotein multimerizes and undergoes a phase transition; the underlying mechanisms and their function are unknown. Here, we show that MYC re-localizes from its canonical location on DNA to RNA in response to the accumulation of intronic RNA. MYC binds RNA directly, which enhances its multimerization. MYC multimers concentrate the nuclear exosome, a 3-5 RNA exonuclease, and its targeting complexes around double-stranded RNA and R-loops, and promote exosome recruitment to R-loops. RNA binding of MYC suppresses activation of the innate immune kinase TBK1. Upon MYC depletion, intron-derived dsRNAs, including RNA derived from repetitive elements and small nucleolar RNAs, accumulate on TLR3, a pattern recognition receptor that activates TBK1. In MYC-depleted cells, TLR3-bound snoRNAs carry aberrant 3-ends, indicating defective exosomal processing. Our data show that the phase transition of MYC is a RNA-driven stress response that suppresses the accumulation of immunogenic RNAs.

molecular biology↗

bioRxiv2023

Association with TFIIIC limits MYCN localization in hubs of active promoters and chromatin accumulation of non-phosphorylated RNA Polymerase II

MYC family oncoproteins regulate the expression of a large number of genes and broadly stimulate elongation by RNA polymerase II. While the factors that control the chromatin association of MYC proteins are well understood, much less is known about how interacting proteins mediate MYCs effects on transcription. Here we show that TFIIIC, an architectural protein complex that controls the three-dimensional chromatin organization at its target sites, binds directly to the amino-terminal transcriptional regulatory domain of MYCN. Surprisingly, TFIIIC has no discernible role in MYCN-dependent gene expression and transcription elongation. Instead, MYCN and TFIIIC preferentially bind to promoters with paused RNAPII and globally limit the accumulation of non-phosphorylated RNAPII at promoters. Consistent with its ubiquitous role in transcription, MYCN broadly participates in hubs of active promoters. Depletion of TFIIIC further increases MYCN localization to these hubs. This increase correlates with a failure of the nuclear exosome and BRCA1, both of which are involved in nascent RNA degradation, to localize to active promoters. Our data suggest that MYCN and TFIIIC exert an censoring function in early transcription that limits promoter accumulation of inactive RNAPII and facilitates promoter-proximal degradation of nascent RNA.

molecular biology↗

bioRxiv2023

Direct RNA-binding by MYCN mediates feedback from RNA processing to transcription control

The MYCN oncoprotein broadly binds active promoters in a heterodimer with its partner protein MAX. MYCN also interacts with the nuclear exosome, a 3-5 exoribonuclease complex, suggesting a function in RNA metabolism. Here we show that MYCN forms stable high molecular weight complexes with the exosome and multiple RNA-binding proteins. In cells, MYCN binds to thousands of intronic RNAs; recombinant MYCN directly binds RNA via a short, highly conserved sequence termed MYCBoxI. Perturbing exosome function results in global re-localization of MYCN from promoters to intronic RNAs. At promoters, MYCN is then replaced by the MNT(MXD6) repressor protein, which inhibits MYCN-dependent transcription. MYCN promotes the degradation of its bound introns via the nuclear exosome targeting (NEXT) complex. Our data demonstrate that MYCN is an RNA-binding protein that regulates nascent transcript turnover and show that competition between its RNA- and DNA-bound states links the dynamics of the MYCN/MAX/MXD network to mRNA processing.

cancer biology↗